Progressive weight loss and wasting are common in HIV disease. The causes of wasting in HIV infection include reduced dietary intake, malabsoption, and ineffective metabolism of nutrients. It is likely that the causes of wasting differ between drug abusers and non-drug abusers because of differences in diet and metabolism. There is little information on the natural history of HIV infection, including nutritional status and wasting in HIV-positive drug abusers. This project will study the nutritional status and causes of wasting in HIV-positive drug abusers in the hispanic community. Emphasis will be placed on the early stages of infection when malnutrition is most amenable to correction. Recruitment of women will receive high priority. Three groups will be studied: Hispanic HIV-positive drug abusers, Hispanic HIV-negative drug abusers and Hispanic HIV-positive non-drug abusers. The three groups will be followed every 6 months for three years during which they will be examined for changes in nutritional, immunological and clinical status. Periodic measures of dietary intake, body composition, energy expenditure, serum vitamin levels, immunologic status, gastrointestinal function, functional status, and quality of life will be taken as the clinical course of the disease is tracked. Identifying the causes of weight loss and wasting at different periods during the course of HIV disease progression will help in the design of targeted nutrition interventions that are appropriate to the drug abusing, HIV-infected population.